trie: implements vlc coder

trie/vlc.go

@@ -0,0 +1,37 @@
+package trie
+
+import "encoding/binary"
+
+type vlcScope struct{}
+
+// vlc implements variable length coding.
+//
+// It's much simpler and a bit faster than RLP.
+// Trie nodes stored in database are encoded using VLC.
+var vlc vlcScope
+
+// AppendUint appends VLC-encoded i to buf and returns the extended buffer.
+func (vlcScope) AppendUint(buf []byte, i uint64) []byte {
+	return binary.AppendUvarint(buf, i)
+}
+
+// AppendString appends RLP-encoded str to buf and returns the extended buffer.
+func (vlcScope) AppendString(buf, str []byte) []byte {
+	buf = binary.AppendUvarint(buf, uint64(len(str)))
+	return append(buf, str...)
+}
+
+// SplitString extracts a string and returns rest bytes.
+// It'll panic if errored.
+func (vlcScope) SplitString(buf []byte) (str []byte, rest []byte) {
+	size, n := binary.Uvarint(buf)
+	buf = buf[n:]
+	return buf[:size], buf[size:]
+}
+
+// SplitUint extracts uint64 and returns rest bytes.
+// It'll panic if errored.
+func (vlcScope) SplitUint(buf []byte) (uint64, []byte) {
+	v, n := binary.Uvarint(buf)
+	return v, buf[n:]
+}